Post by callmerob on Nov 2, 2023 16:56:56 GMT -5
Stumbled across this on Amazon…
Lawnmower blade grinder
The company Oregon has been around for awhile. Grampa Cox invented the first good chainsaw in 1947, and they’ve been making tools ever since. This lawnmower blade grinder is a lightweight bench-top model, and it does a lot of things right. Motor is 1/3hp, 1725rpm, 1” motor shaft, 5/8” arbor, swinging an 8” grinding wheel, with vertical adjustment, welded steel frame, switch, plug it in.
But I want a saw more than a grinder. My DIY drop-saw with little toy motors is too slow and feeds too heavy. And isn’t a diamond saw just a skinny grinding wheel anyway? Maybe it could make all those cuts on sphere preforms.
In any case, it has a lot of what a saw needs, already assembled. Priced at $287.
So I bought it.
Couldn’t help myself.
Don’t Drink & Shop, kids.
Replace the grinding wheel with a saw blade. Build a simple vise and sliding table. Push the rock into the blade. Should be fun, yeah?
The raised steel platform means not enough room for a rock, so remove it. We can cut the horizontal braces with a hacksaw, and the welds with a grinder. Must wear eye protection. This is not pretty and is harder than it looks - dirty, noisy, slow, not enough room for either tool. Not nearly as much fun as the movie in my head.
Ok this part is fun.
Grind the weld remnants & repaint.
Base plate & drawer slides
Sliding table is 1/2” PVC plate.
Assembled sliding table, drawer slides, vise
Saw blade is 8” x 0.080” x 5/8 hole.
Flange washers for a Skil saw.
Flood coolant is drip irrigation.
Fountain pump in a bucket.
Scatter shield is heavy steel for a grinding wheel.
Tilt the saw and the table rolls downhill.
Increase the angle to increase the feed force.
Down an incline the forces are Fgravity, Fparallel, and Fperpendicular. Something sine angle, something cosine angle, something, minus Ffriction, something.
I don’t know if this works but let’s cut a rock, shall we?
3” obsidian rough.
Tiles make a mold.
Plaster-of-Paris holds it square.
All up.
In the cabinet.
Rough estimates:
Tilt = ~20 degrees
Feedrate = ~3” per ~3 hours
It keeps hanging up on the flood coolant or a clamp or a hose gets loose or something. Each is a different dumb teething problem. We call it ‘prototype development’ to feel better about it.
Blade is square to the table. Not-quite-a-square measures 3.00” plus/minus 0.10”. Not quite square because of initial setup errors.
Not-quite-a-cube either. Sides are skewed slightly. All 4 sides are square with the table, but not quite square with each other. Table slides may need adjustment, or the motor shimmed, but it may not be enough to matter.
A 3” cube is 4” diagonally, and fixtures add a little more, so raise the motor for clearance. Please see the new position of the red bolts. Add shims to raise the scatter shield.
V-blocks
The white shim in the v-block positions the rock for the cut and keeps the v-block clear of the blade.
First octagonal cut
Three more cuts make an octagon.
Sixteen trim cuts make an octahedron.
Same fixture.
The not-quite-an-octahedron.
(photo is distorted - it looks better IRL)
That’s all the sawing. The preform is hand ground on a diamond wheel to round the sharp corners before it goes to the sphere machine. It’s my first obsidian. You always remember your first obsidian. If you’re interested, here’s a link to the sphere thread….
forum.rocktumblinghobby.com/thread/103840/3-obsidian-sphere
I think the octahedron is uneven because of operator error.
It’s a fun little tilt-saw, and works ok with baseball-size rocks. It is cutting a lot better than the last DIY, and it meets my weird situation where the saw lives in a cabinet on the patio. We will see if the drawer slides survive. WD-40 rinse and fingers crossed.
I like this Black Widow saw blade. The saw is cutting 3” obsidian, and that’s encouraging enough to try some serpentine next. I’m pleased it even works at all.
Tilt-O-Matic.
Hope you like it.